sustainability Article Improved Serviceability and Environmental Performance of One-Way Slabs through the Use of Layered Natural and Recycled Aggregate Concrete Nikola Toši´ c 1, * , Snežana Marinkovi´ c 2 and Yahya Kurama 3 1 Civil and Environmental Engineering Department, Universitat Politècnica de Catalunya, Jordi Girona 1–3, 08034 Barcelona, Spain 2 Faculty of Civil Engineering, University of Belgrade, Bulevar kralja Aleksandra 73, 11000 Belgrade, Serbia; [email protected] 3 Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA; [email protected] * Correspondence: [email protected] Received: 12 November 2020; Accepted: 7 December 2020; Published: 9 December 2020 Abstract: Recycled aggregate concrete (RAC), i.e., concrete produced with recycled concrete aggregate (RCA) has been heavily investigated recently, and the structural design of RAC is entering into design codes. Nonetheless, the service load deflection behavior of RAC remains a challenge due to its larger shrinkage and creep, and lower modulus of elasticity. A novel solution to this challenge is the use of layered concrete, i.e., casting of horizontal layers of different concretes. To investigate the potential benefits and limits of layered concrete, this study contains a numerical parametric assessment of the time-dependent sustained service load deflections and environmental impacts of homogeneous and layered NAC and RAC one-way slabs. Four types of reinforced concrete slabs were considered: homogeneous slabs with 0%, 50% and 100% of coarse RCA (NAC, RAC50 and RAC100, respectively) and layered L-RAC100 slabs with the bottom and top halves consisting of RAC100 and NAC, respectively. In the deflection study, different statical systems, concrete strength classes and relative humidity conditions were investigated. The results showed that the layered L-RAC100 slabs performed as well as, or even better than, the NAC slabs due to the differential shrinkage between the layers. In terms of environmental performance, evaluated using a “cradle-to-gate” Life Cycle Assessment approach, the L-RAC100 slabs also performed as well as, or slightly better than, the NAC slabs. Therefore, layered NAC and RAC slabs can be a potentially advantageous solution from both structural and environmental perspectives. Keywords: construction sustainability; functionally graded concrete; Life Cycle Assessment; OpenSees; sustained service load; time-dependent deflection 1. Introduction The use of recycled concrete aggregate (RCA) in the production of recycled aggregate concrete (RAC) is a promising way of addressing the sustainability challenges of concrete construction. However, most RCA is used for non-structural applications such as backfilling, road base and sub-base [1], with only less than about 10% being used for new concrete. One source of concern toward the structural use of RAC is its time-dependent behavior under service loads. Namely, due to the residual mortar attached to RCA, RAC exhibits a lower modulus of elasticity [2] and higher shrinkage and creep [3,4], which causes increased deflections of reinforced concrete (RC) structures. For example, Toši´ c et al. [5] showed that analytical models for deflection control need to be modified to take into account the greater deformations of RAC, and Toši´ c and Kurama [6] performed a parametric numerical Sustainability 2020, 12, 10278; doi:10.3390/su122410278 www.mdpi.com/journal/sustainability
Improved Serviceability and Environmental Performance of One-Way Slabs through the Use of Layered Natural and Recycled Aggregate Concrete
Jul 01, 2023
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